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DOE OSTI2021

Challenging problems of quality assurance and quality control (QA/QC) of meteorological time series data

Abstract Representativeness and quality of collected meteorological data impact accuracy and precision of climate, hydrological, and biogeochemical analyses and predictions. We developed a comprehensive Quality Assurance (QA) and Quality Control (QC) statistical framework, consisting of three major phases: Phase I—Preliminary data exploration, i.e., processing of raw datasets, with the challenging problems of time formatting and combining datasets of different lengths and different time intervals; Phase II—QA of the datasets, including detecting and flagging of duplicates, outliers, and extreme data; and Phase III—the development of time series of a desired frequency, imputation of missing values, visualization and a final statistical summary. The paper includes two use cases based on the time series data collected at the Billy Barr meteorological station (East River Watershed, Colorado), and the Barro Colorado Island (BCI, Panama) meteorological station. The developed statistical framework is suitable for both real-time and post-data-collection QA/QC analysis of meteorological datasets.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2023

Metal–Organic Frameworks: Challenges Addressed via Magnetic Resonance Spectroscopy

Magnetic resonance spectroscopies occupy a premier position within the chemical sciences by revealing structure and dynamics in molecules and solids associated with photosynthesis, enzymology, Alzheimer proteins, pharmaceuticals, catalysts, polymers, and electronic materials. Here, we review the recent literature contributions of NMR and EPR spectroscopy towards the study of metal–organic frameworks from 2017 to mid-2022. We organize the review around what we perceive to be the intellectual challenges in MOF research: structure, dynamics, synthesis, properties, and function.

47 OTHER INSTRUMENTATION↗

DOE OSTI2020

Revisiting the first Sandia Fracture Challenge with transient deformation heating and strain localization considerations

In this study, we present a systematic experimental study and accompanying theoretical analysis of the dependence of ductile fracture on strain localization, strain hardening rates, deformation-induced thermal softening, and transient heat conduction under spatially uniform as well as spatially heterogeneous deformation. Spatially uniform cases are studied via standard dogbone shaped specimens subject to uniaxial tension. Spatially heterogeneous deformation is studied via the so-called Sandia Fracture Challenge (SFC) specimen, which is a standard compact tension specimen modified with three machined holes in front of a blunt notch. We utilize the same precipitation hardened martensitic stainless steel used in the first SFC experiments, i.e. 15-5 PH with an H1075 heat treatment. We also study 15-5 PH in Condition A and with the H900 heat treatment, each of which has a different hardening behavior and ductility. We find that the ductility does not correlate with the deformation to first crack initiation in the SFC specimen. Instead, hardening rates are better correlated. Moreover, a re-examination finds that an accurate calibration of the hardening rates is strongly correlated with accurate blind predictions of ductile fracture in the SFC specimens. Given that thermal softening can greatly affect hardening rates, we provided a thermographic analysis of deformation-induced heating and transient heat transfer in both the dogbone shaped samples and the SFC specimens. Transient heating in stainless steels is found to have first-order effects on the strain at the onset of necking, strain to fracture, as well as strain localization and ductile fracture in complex geometries even under so-called quasi-static loading rates.

42 ENGINEERING↗

DOE OSTI2024

Challenges, progress, and future perspectives for cyanobacterial polyhydroxyalkanoate production

Polyhydroxyalkanoates (PHA) are a promising bio-based alternative to traditional plastics derived from petroleum. Cyanobacteria are photosynthetic organisms that produce PHA from CO 2 and sunlight, which can potentially reduce production costs and environmental footprint in comparison to heterotrophic bacteria cultures because (1) they utilize inorganic carbon sources for growth and (2) they do not require intensive aeration for oxygenation. Moreover, supplementing precursors such as propionate, acetate, valerate, etc., can be used to obtain various copolymers with plastic customizable properties in comparison to the classical homopolymers, such as polyhydroxybutyrate, PHB. This critical review covers the latest advances in PHA production, including recent discoveries in the metabolism interplay between PHA and glycogen production, and new insights into cultivation strategies that enhance PHA accumulation, and purification processes. This review also addresses the challenges and suggests potential solutions for a viable industrial PHAs production process.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2022

Assessing the Effectiveness of Large-Scale Environmental Restoration: Challenges and Opportunities

A recent National Academies consensus report addresses monitoring and assessment of cumulative effects of large-scale and multiple restoration projects within the context of long-term environmental change. Fines and penalties from the Deepwater Horizon oil spill in the Gulf of Mexico (GoM) have supported hundreds of restoration projects at spatial scales not often possible in the past. Here, in this paper, the report committee members and staff provide personal reflections from our time working on the study. We found that gaps in data collection, issues with data accessibility, and a lack of synthesis and analysis are hindering the ability to answer a basic question: What are the impacts of these many restoration efforts on improving ecosystem health and productivity in the GoM at the regional and Gulf wide scale? Restoration efforts are occurring in environments where many trends are changing and exhibiting higher variability than in the past, suggesting that previously successful restoration practices may no longer be adequate to compensate for the effects of environmental changes and variability. Our proposed approach to these challenges includes employing emerging monitoring technologies; using conceptual models; devising an adaptive management framework; rethinking restoration outcome goals; assessing cumulative effects; and undertaking rigorous synthesis and analysis of existing information on long-term environmental trends and restoration efforts. Restoration scientists and practitioners working in the GoM have an unprecedented opportunity to demonstrate large-scale environmental recovery if advances in monitoring, synthesis, assessment, and action are taken quickly. We are cautiously optimistic that, with mid-course adjustments, continued progress toward large-scale environmental recovery is possible.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2022

Challenges and Opportunities of Integrating Electric Vehicles in Electricity Distribution Systems

Increased charging needs from widespread adoption of battery electric vehicles (EVs) will impact electricity demand. This will likely require a combination of potentially costly distribution infrastructure upgrades and synergistic grid-transportation solutions such as managed charging and strategic charger placement. Fully implementing such strategic planning and control methods - including business models and mechanisms to engage and compensate consumers - can minimize or even eliminate required grid upgrades. Moreover, there are also opportunities for EV charging to support the grid by helping solve existing and emerging distribution system challenges associated with increasing distributed energy resources (DERs) such as solar generation and battery energy storage. This paper reviews the potential impacts of EV charging on electricity distribution systems and describes methods from the literature to efficiently integrate EVs into distribution systems.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2021

Recalibrating Best Practices, Challenges, and Limitations of Estimating Tree Transpiration Via Sap Flow

Purpose: Transpiration dominates hydrologic fluxes from terrestrial ecosystems to the atmosphere. Sap flow is the most widely used method to quantify transpiration, and calibrations can improve the accuracy of these estimates. Despite numerous suggestions to perform and apply sap flow calibrations, seemingly few reports apply these recommendations. Here, we sought to determine the prevalence of calibration across sap flow methodology. Recent Findings: In this work, we reviewed tree sap flow literature over the past nine years and determined that only 5.3% of these publications documented the performance of calibrations, the application of coefficients from previous calibrations, or the application of correction factors using calibration data to ensure or improve accuracy of transpiration estimates. These data indicate that calibration has not been adopted as a best practice. However, these data may also reflect challenges to the performance and application of calibration indicating fundamental limitations of sap flow methods. Summary: We highlight the need for testing critical assumptions regarding calibration; specifically, that coefficients derived from calibrations on small stems are suitable for application to large stems and that different calibration approaches yield similar transpiration estimates. We encourage researchers to adopt calibration as a best practice for sap flow data and to explain how calibration was performed, how calibration data were applied, and to acknowledge and justify circumstances that preclude or do not necessitate calibration. Without the adoption of calibration and an improved understanding of its limitations, our understanding of transpiration and ability to quantify it using this technology will remain inadequate.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2021

Challenges in Monte Carlo Event Generator Software for High-Luminosity LHC

Abstract We review the main software and computing challenges for the Monte Carlo physics event generators used by the LHC experiments, in view of the High-Luminosity LHC (HL-LHC) physics programme. This paper has been prepared by the HEP Software Foundation (HSF) Physics Event Generator Working Group as an input to the LHCC review of HL-LHC computing, which has started in May 2020.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2020

Challenges and Development of Tin-Based Anode with High Volumetric Capacity for Li-Ion Batteries

Abstract The ever-increasing energy density needs for the mass deployment of electric vehicles bring challenges to batteries. Graphitic carbon must be replaced with a higher-capacity material for any significant advancement in the energy storage capability. Sn-based materials are strong candidates as the anode for the next-generation lithium-ion batteries due to their higher volumetric capacity and relatively low working potential. However, the volume change of Sn upon the Li insertion and extraction process results in a rapid deterioration in the capacity on cycling. Substantial effort has been made in the development of Sn-based materials. A SnCo alloy has been used, but is not economically viable. To minimize the use of Co, a series of Sn–Fe–C, Sn y Fe, Sn–C composites with excellent capacity retention and rate capability has been investigated. They show the proof of principle that alloys can achieve Coulombic efficiency of over 99.95% after the first few cycles. However, the initial Coulombic efficiency needs improvement. The development and application of tin-based materials in LIBs also provide useful guidelines for sodium-ion batteries, potassium-ion batteries, magnesium-ion batteries and calcium-ion batteries. Graphic Abstract

25 ENERGY STORAGE↗

DOE OSTI2021

Recent developments on 2D magnetic materials: challenges and opportunities

The emergence of two-dimensional (2D) magnetic materials exhibiting strong magnetization at ultrathin limits above room temperature are promising for miniaturization of devices beyond Moore’s law for future energy efficient nano-electronic devices. Here, the current status, different mechanisms for the existence of magnetism, spin current injection and other magnetic properties of monolayer to few-layers of various 2D magnetic materials are reviewed. Some of the promising applications of these materials are spintronics devices such as spin valves, spin tunnel field-effect transistors, and spin filtering magnetic tunnel junctions. Due to the tunable electronic properties of these 2D materials, it's quite interesting to inject the spin current with suitable ferromagnetic contacts. For instance,black phosphorus is a layered material with a small Schottky barrier height capable of injecting spin current. This review includes many recently explored 2D magnetic materials ranging from exfoliated 2D crystals to CVD grown materials from single to several layers, demonstrating tunable layer dependent magnetic properties. We also explore some of the promising theoretical study based on 2D magnetic compounds such as 2D alkali-based chromium chalcogenides, which shows ferromagnetic as well as semiconducting behavior. The layer-dependent magnetic ordering has been observed in layered compounds like 1T-CrTe 2 , VSe 2 , CrI 3 , and Fe 3 GeTe 2 , which have great potential for the future applications in magnetic based electronic devices. Finally, we emphasize the challenges, opportunities and future directions of the 2D magnetic materials, where new discoveries might have outstanding impact in transformational scientific breakthroughs towards memory, spintronics, optoelectronics and other multifunctional device applications.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Integrating renewable energy into mining operations: Opportunities, challenges, and enabling approaches

Mining is one of the most energy-intensive industries worldwide. It also provides a critical source of raw materials for the manufacturing, transportation, construction, and energy sectors. Demand for raw materials is projected to increase as the world population grows and many low-income economies become middle-income countries. This growth in mineral demand, coupled with falling mineral ore grade, will likely increase the mining industry’s energy demand, used for activities across exploration, extraction, beneficiation and processing, and refining. At the time of this writing, mine operations are – due to their remoteness – dependent on fossil fuels such as diesel, heavy oils, and coal. In principle, mining could use energy recovery, renewable energy, and carbon capture to supplement, replace, or mitigate the impacts of fossil fuel use. However, a combination of renewable-energy technologies would be required. We explore challenges, opportunities, and enabling approaches to integrate renewable energy technologies into mining operations by examining the literature, including academic work, technical reports, and data produced by international agencies. Here, we find that despite numerous opportunities, technical issues still need to be considered, but solutions can tailor renewables to the mining industry. Further research should focus on identifying specific opportunities, technologies, and implementation strategies across the value chain of a variety of minerals with similar operational procedures.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2026

Revolutionizing thermal Management in Next-Generation AI data centers: Challenges and breakthrough innovations

Data centers (DCs) serve as critical infrastructure for powering the growth and evolution of AI. Next-generation AI DCs present unique challenges in thermal management driven by unprecedented computational demands. This paper provides a comprehensive summary of key stakeholder perspectives on technology gaps, infrastructure requirements, test bed needs, emerging opportunities, and preliminary solutions related to thermal management for AI DCs. It establishes six strategic pillars of thermal management for next generation AI DC: reliability, deployability, efficiency, resilience, measurability, and valorization. The discussion spans a range of critical topics, including advanced cooling technologies, thermal strategies for emerging modular and edge DCs, system-level optimization and control frameworks, infrastructure planning and grid integration designs, benchmarking approaches, and pathways for waste heat recovery and reuse. The proposed research, development, and demonstration efforts are aimed at accelerating the deployment of AI DCs while ensuring energy efficiency, reliability, safety, and regulatory compliance.

Wang, Pengtao [ORNL] (ORCID:0000000214713429)↗

DOE OSTI2025

A critical review of electrochemical heat pump technologies: Status, challenges, and perspectives

The development of advanced heat pump technologies is critical for reducing global energy consumption in the building sector, where space heating and cooling account for nearly 50% of energy use. Electrochemical heat pumps (EHPs) offer a promising alternative to vapor compression systems by enabling direct electrochemical-to-thermal energy conversion, often with environmentally benign working fluids that exhibit low or zero global warming potential (GWP). Prior literature has predominantly focused on chemically reactive heat pumps, while comprehensive assessments of electrochemical mechanisms remain limited. Here, this review addresses this gap by systematically evaluating the underlying principles, architectures, and performance metrics of EHP systems. Compared to conventional vapor compression systems, EHPs can achieve 10%-30% higher energy efficiency, with reported cooling coefficients of performance (COP c ) ranging from 3.5 to 14.3 under standard operating conditions. Despite these advantages, widespread adoption is hindered by challenges including membrane degradation, electrode fouling, sluggish redox kinetics, and elevated system-level capital costs. To address these limitations, the review outlines three research priorities: (i) the development of advanced membranes, catalysts, and electrode materials with enhanced chemical and mechanical stability; (ii) the application of molecular-level simulations for the rational design of high-performance redox-active working fluids; and (iii) the integration of advanced diagnostic techniques for real-time monitoring and sustained operation of EHPs. By consolidating recent advances and explicitly identifying technological and scientific gaps, this work uniquely contributes a comprehensive framework for guiding future electrochemical heat pump research and facilitating the transition to sustainable thermal management technologies.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2025

A framework for challenges and solutions in biodesign research

The bioeconomy represents an advanced economic paradigm that builds upon previous agricultural, industrial, and digital economic models. It seeks to tackle critical global challenges such as resource scarcity, escalating healthcare demands, and environmental degradation. At the heart of the bioeconomy is biomanufacturing, which uses natural or engineered enzymes or cell factories built from biological components like promoters, terminators, regulatory sequences, reporters, and functional genes into various chassis hosts (including animal, microbial, plant, and de novo systems) to create products such as food, energy, medicine, materials, chemicals, and engineered tissue/organs. An enabler of biomanufacturing is biodesign – also known as biosystems design and closely related to synthetic biology or engineering biology. This interdisciplinary field aims to understand and predictably modify existing life forms or create entirely new biological entities/systems using rational engineering strategies and automated design tools. Through these capabilities, biodesign supports the discovery, optimization, and creation of efficient platforms for biomanufacturing.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2023

Applications of biomass-derived solvents in biomass pretreatment – Strategies, challenges, and prospects

We report biomass pretreatment is considered a key step in the 2nd generation biofuel production from lignocellulosic biomass. Research on conventional biomass pretreatment solvents has mainly been focused on carbohydrate conversion efficiency, while their hazardousness and/or carbon intensity were not comprehensively considered. Recent sustainability issues request further consideration for eco-friendly and sustainable alternatives like biomass-derived solvents. Carbohydrate and lignin-derived solvents have been proposed and investigated as green alternatives in many biomass processes. In this review, the applications of different types of biomass pretreatment solvents, including organic, ionic liquid, and deep eutectic solvents, are thoroughly discussed. The role of water as a co-solvent in these pretreatment processes is also reviewed. Finally, current research challenges and prospects of utilizing biomass-derived pretreatment solvents for pretreatment are discussed. Given bioethanol's market potential and increasing public awareness about environmental concerns, it will be a priority adopting sustainable and green biomass pretreatment solvents in biorefinery.

09 BIOMASS FUELS↗

DOE OSTI2023

Growth of carbon nanotube forests on flexible metal substrates: Advances, challenges, and applications

Owing to their remarkable properties and ordered architecture, vertically aligned CNT forests (VACNT) hold promises for countless applications ranging from energy storage to multifunctional fiber production. Over the last three decades, studies of carbon nanotube (CNT) growth have provided invaluable insight into the CNT nucleation and growth mechanism and enabled critical advancements in nanotechnology. Nevertheless, the ability to fully harness the exceptional VACNT properties in commercial devices is bottlenecked by compatibility of current CNT synthesis processes with large-scale manufacturing. Metal foil substrates present an economic alternative to traditional insulating substrates, like silicon or quartz, and are compatible with both roll-to-roll and automated, large-scale, batch processes. Compared to CNT growth on Si substrates, metal foils present additional challenges, such as increased roughness and reactivity at high temperatures. Nonetheless, many successful VACNT growths on conducting metal foils have been reported, which demonstrate the feasibility of metal substrate use for large-volume production of high-quality CNTs. Here, in this review, we discuss advancements in the field of VACNT growth on metal foil and specifically examine different choices for metal substrates, barrier and catalyst layers, deposition and growth methods, resulting CNT characteristics, and highlight a number of applications that benefit from CNT growth on metal substrates and transition to large-scale manufacturing.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Audacity of huge: overcoming challenges of data scarcity and data quality for machine learning in computational materials discovery

Machine learning (ML)-accelerated discovery requires large amounts of high-fidelity data to reveal predictive structure–property relationships. For many properties of interest in materials discovery, the challenging nature and high cost of data generation has resulted in a data landscape that is both scarcely populated and of dubious quality. Data-driven techniques starting to overcome these limitations include the use of consensus across functionals in density functional theory, the development of new functionals or accelerated electronic structure theories, and the detection of where computationally demanding methods are most necessary. When properties cannot be reliably simulated, large experimental data sets can be used to train ML models. In the absence of manual curation, increasingly sophisticated natural language processing and automated image analysis are making it possible to learn structure–property relationships from the literature. Finally, models trained on these data sets will improve as they incorporate community feedback.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Recent advances and challenges in optimization models for expansion planning of power systems and reliability optimization

Optimization models for expansion planning of power systems aim to determine capacities, investment timing, and location of power systems to satisfy the power demands while minimizing the total cost. The models have become complex in recent years to reflect both regulations on conventional energy sources and the increasing penetration of renewable energy sources (RES). This paper reviews the basic concepts and optimization models for expansion planning of power systems. We first explain the definition and features of generation expansion planning (GEP), transmission expansion planning (TEP), and generation and transmission expansion planning (GTEP). To address the computational challenges of large-scale expansion planning problems, we review several simplifications including temporal and spatial aggregation, and decomposition methods. This paper also addresses power system reliability defined as the probability of satisfying the load demand while withstanding failures of components. Finally, the goal of this paper is to provide a research overview, discuss trends in expansion planning of power systems, and suggest directions for future research.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗